Drill bit



6.15:. Vlm-:BENSEN `2,228,482.

Jan. 14, 1941.v

DRILL. BIT

Original Filed June *18, 19'37 5 .ASheets--Sheei'l 1 3 Sheets-Sheet 2DRILL BIT G. IE. PREBENS'EN Original Filed June 18,

Jan. 14, 1941.

22u31 HV-l. 1% 1 7,@

Jan. 14, v1941.

G. E. FREBENSEN DRILL BIT Orig-ina). Filed June 18, 1957 3 SheeJcs-Sheet3 4 Vrn Hl W Ammann f Arme/lex Patented inn. 14, 1941 DRILL BIT Gary E.Ptebensen, Los Angeles, Calif., assigner to The Speedrill Corporation,Los Angeles, Calif., a corporation'of Delaware Application June 18,1937, Seriall No. 148,942

`Renewed June 3, 1940 This invention 'relates t drilling bits of thetype commonly employed-for drilling oil wells, and has for an object theprovision of a drill of. improved design through the use of which thedrilling of an oil well or similar deep hole through different types offormations and under various conditions of operation is greatlyfacilitated and expedited, andmade materially-less expensive andgenerally more advantageous than. has been possible when using any ofthe various types of drillingbits which heretofore have `been available.

A more detailedobject ofthe present invention is the provision of awell-drilling bit which is capable of operating according to thelwellknown rotary principle or, when occasion demands, is converted tooperate inl accordance with the principle of percussion, i. e.,according to the principle of drilling wherein a formation is shatteredand chipped away as the result of the imposition of a heavy and abruptblow or percussive force upon the drill.

Another. object is to provide a drilling apparatus of the characterdescribed which is self-regu# vlating to the extent that as long as thebit is operating in that type of formation which is 4most easily erodedby rotary action, the bit will rotate; but as the bit encounters hardermaterial, a part of the rotative energy imparted tothe bit by the drillstem is translated into percussive energy to be exerted by the bitagainst the formation.

j is made manifest to the drilling operator, sor

It is another Aobject in this same connection, therefore, to providea'bit, the action of which which strikes the bit in order to develop thedesired percussive forces.

A 'still further object is to provide, in a' drill tool of the characterdescribed, means whereby .the bit is frequently lifted from the .bottomof the hole or, if not actually so lifted, the pressure of .the bit onbottom so greatly relieved that ciriculation fluid is given'increasedopportunity to wash under and past the cutting'edges -of the bit, forthe manifold purpose of cooling those cutting edges and washing away thedetritus and eration in the design of the drilling tool of the presentinvention.

The invention possesses other objects and fea-l .tures of advantage,some of which, with those enumerated, will be set forth in the followingdescription of the particular embodiment of my invention which isillustrated in the drawings accompanying and forming4 a portion' of thespecification. It is to be understood that I do not limit myself totheshowing made by the said drawings and description, as I may adoptvariations of the preferred` form lWithin thescope of my inventionas.set forth in the claims.

Referring to the drawings: Fig. l is a view, partially in side elevationand partially in vertical section, of a drilling bit embut showing thecam element separated.

i Figs. 4, 6 and 6 are enlarged vertical medial sectional views showingthe upper. middle 'and desiderata which have been taken into considlowerportions, respectively, of a bit embodyingv the principles of thepresent invention. These views are in reality a single 4view broken intothree sections.

Fig. 7 is a transverse sectional view,taken upon the line 'I-1 of Fig.4, with the direction of view as indicated.

Fis. 8 is a transverse sectional view taken upon the line 8l of Fig. 5,with the direction of view asindicated. l.

Fig. 9 is a transverse sectional view taken upon the line 9-9 of Fig. 6,with the direction of view as indicated.

Fig. 10 is a view similar to Fig. 6 but showing the cam elements in sideelevation and in their most closely interconnected position.

Fig. 11 is a view similar to Fig. 10 but showing the cam elements in agreater degree of separation.

Fig. 12 is a perspective view of the cam elements alone. l

The` drawings illustrate one embodiment of the present inventionoperatively connected to the lower end of a drill stem 2| by anysuitable means, such as .a tool joint 22 comprising threadedlyinterconnected pin and box members 23 and 24 respectively. Secured tothe lower end of the box member 24 is a relatively long tube 26, thebore 21 of which is at all times in communication with the bore 28 ofthe drill stem 2|, inasmuch as both the pin 23 and the box 24 of thetool joint 22 are hollow. The major portion of the tube 26 istelescopically disposed within a cover tube 3| and suitable packing 32establishes a fluid-tight seal between the cover tube 3| and the tube 26which, for the sake of convenience, will hereinafter be termed thetelescoping tube. Packing 32 is conined between a retaining ring 33rigid withthe cover tube 3| and a gland nut 34 threaded into the upperend of the cover tube.

The cover tube 3| extends substantially throughout the entire length ofthe drill, its lower end being rigidly connected to the drilling bit 36,preferably by being threadedly engaged upon the box member 31 of thecoupling 38, the pin member 33 of which is preferably an integralportion of the bit 36. e

The box member 31 is provided with an upwardly extending threaded pin4|, by means of which the lower cam member 42 is rigidly screwed to thecoupling 38 and hence to the pin 36. Cooperatively associated with thelower, or anvil, cam v42 is an upper or hammer cam 43. These cams. 42and 43 are best shown upon Figs. 10 to 12, inclusive. Each is preferablyprovided with a plurality of sloping surfaces 44 terminating in anabrupt shoulder 46 on each cam member 42, 43.

vThe sloping surfaces 44 all slope in the same direction around the'axisof that cam member. The teeth 44, 46 of the other member arecomplementarily formed so that when the cam members 42, 43 are in theirposition of most intimate engagement (Fig. 10), the two cam elements fitnicely together. Rotary drilling normally being accomplished by a rotarymotion of the drill in a clock-wise direction, the parts are so arrangedthat when the upper, hammer cam member 43 turns in a clock-wisedirection with respect to the lower, anvil cam, the sloping surfaces ofthe upper cam member 43 will slide upon the sloping surfaces of thelower cam member, raising the upper cam member 43 away from the lowercam member 42 (Fig. l1). This will continue until the crests of theteeth of the upper cam member passj the crests of the teeth of the lowercam member, whereupon lthe upper, hammer cam 43 will drop forcibly uponthe lower cam 42, imparting (by'means of its weight and spring elementsto be described hereinbelow) a severe blow or percussive force to thelower anvil cam 42, which percussive force is transmitted directly tothe bit 36.

Secured to the upper end of the upper cam member 43 is a. `coupling 5|to which is rigidly secured as by threads 52- a tube 53, the bore ofwhich is provided with splines 54. These splines 54 provide means forconnectingthe tube 53 with the telescoping tube 26 in such a manner thatthe two tubes are locked together for rotation but for free telescopingmovement with respect to cach other, preferably the tube 26 beingdisposed inside the tube 53. Whereas any suitable means for establishingthe splined interconnection between these two tubes 26 and 53 may beemployed, the embodiment shown utilizes a suitable length of tubing 56which is rigidly secured to the outside of the telescoping tube 26 as bybeing shrunk thereon. Splines 51 complementary to and slidably engagedwith the splines 54 of the tube 53 are formed upon the outer surface ofthe tube 26. Hence it becomes apparent that whereas a limited degree oivertical movement of the drill stem 2| is permitted withoutcorresponding vertical movement of the upper cam 43 although the cam 43is caused to rotate at all -times with the drill stem 2|.

However, any lowering movement of the drill stem 2| with respect to theupper cam 43 is resisted by a relatively heavy coil spring 6| which isunder compression between the coupling 5| and any suitable means, suchas a threaded pin 62, providing'an abutment rigid with the lower end ofthe telescoping tube 26. This same threaded pin 62 also 'provides aconvenient abut,- ment for the lower end of another compression -spring63, the 'upper end of which is continually pressing upwards against theadjustable collar 64.- This collar 64 is adjustably secured, as by asuitable set screw 66 adjacent the upper end of the tube 61, which issuitably disposed inside the telescoping tube 26. Moreover, the tube 61is open at its upper end to the bore of. the telescoping tube 26, sothatthe circulation iiuid which is provided at relatively high pressureswithin the bore 28 and the drill stem is at all times available withinthe bore of the tube 61 also. Consequently this tube will hereinafter betermed the circulation tube. It communicates at its lower end (.see Fig.6) with the bore of the coupling 38, and thence with a suitable axialhole 69 in the bit 36. From the hole 69 preferably a plurality of orices1| ,conduct the circulationfluid to the exterior of the bit 36,delivering the fluid preferably between the ilukes 12 in theconventional manner. Inasmuch as vertical movement of the circulationtube 61 with respect to the telescoping tube 26 occurs when the uppercam 43 rides over the lower cam 42, suitable packing means 13 areinterposed between the telescoping tube 26 and the circulation tube 61,this packing 13 being cornpressed between suitable compression rings 14and 16 threadedly engaged upon the circulation tube 61 adjacent itsupper end. This lpreventsy the leakage of circulation fluid into thechamber' 11 between the circulation tube 61 and the telescoping tube 26.It is within this chamber 11 that' the compression spring 63 isdisposed. Inasmuch vas this compression spring 63 is at all timespressing upwards against the `collar 64 Iwhich is rig-id with thecirculation tube 61, this tube is at all times urged upwards with re*`ect to the same member (the threaded pin 62 which issecured to thelower end of the telescoping tube 26) as that against which the upperend of the larger spring 6| presses. The lower end of 'the circulationtube 61 being rigidly connected As stated, the upper side of the chamber11 is closed by the packing 13. The pin 62 against which the springv63presses has a bore 82 looseenough to present a material degree ofclearance between the pin 62 and theouter circumference of thecirculation tubel 61, hence communication is established. at all timesbetween the chamber 11 and the chamber 83 immediately therebelow, withinwhich the larger spring' 6| isdisposed. Both these chambers are keptlled with a suitable lubricant which is permitted to penetrate to thecam surfaces through the expedient of suitable oil holes 84 extendinglongitudinally through the coupling'Sl 'and through the bore 86 ofthecam members' 42-and 43, which is sumciently larger than the outercircumference of the circulation tube 61 to permit such oil penetration.This same body of lubricant also is permittedA to penetrate to thesplines 54, 56, through the expedient of an oil holev 9| in the wall ofthe telescoping tube 26 adjacent the upper end of the chamber 11; andlubricant is also permitted to penetrate to the space between the covertube 3| and the tube 53 by-means of an oil hole 92 in the tube 53,preferablyA adjacent the upper end of the chamber 83. l y

It becomes apparent, therefore, that the drilling tool of the presentinvention comprises a body made up of upper and lower body portions, i.e.,

of upper and lower cams 43 and 42, respectively, -wh1ch are continuallyurged into engagement with each other by the springs 6| and 63. The

parts are so disposed that, although the engag- 1 ing surfaces of thesecams are inclined, the

springs force them together with suiilcient pressure-to cause the bit 36to be turned by the upper part of the body, which ofcourse is rotated inthe conventionarmannerby the drill stem 2| being connected thereto bythe' splines 54 and 56 and the telescopic tube 26 as explained here'-inabove. Accordingly, when the drill is being operated, in`fairly loosematerial, such as oil sand, gravel or .the like, offering comparatively'little resistance to the rotation of .the bit 36,-the bit will rotatein the same manner as a convento. Obviously, this tendency is resisted.-by the spring6l, but when the force-resisting rotation of the bit 36becomes sufficient to reduce the.

speed at which the bit 36 rotates to less than that at which the drillstem is rotating, the cams of the upper portion 43 of the body of thedrill will ride upwards along the inclined surfaces of the cam of thelower part of the body42 (see Fig. 11)

' until the crests of the upper camspass 'the crests of the lower cams,at which; time the spring 6I will force the upper part 43 of the bodydownward with great force and coliisiderable speed,v

causing the upper part of the' body to strike the lower part and thusdeveloping a large percussive force, tending to drive the cutting edgesof the vertical, Ito follow the slope of the hardstratum. However, whenthe bit of the present invention encounters such a hard stratum, thecutting edges at just one side of the bit will rst encounterv that hardmaterial, causing the bit immediately to be slowed in its rotativemovement, bringing the hammering or percussive action of the cam intoplay which, as explained, produces the chipping and gouging action ofthe cutting edges of the bit against the sloping stratum. This occursbefore the bit has been given opportunity to deflect from the truevertical, i. e., when the body of the bit is still guided in a verticalhole, and inasmuch as the operator is advised ofthe type of stratumwhich his bit has encountered, he is given the opportunity to slow downthe rate at which the draw works pays out cable to lower the` drillstem, thus permitting the now chipping .bit to penetrate the slopingsurface of the hard stratum before time is allowed for it to bedeflected by that stratum-from the vertical.

Another advantage of the bit of the present invention is that when thecrests of the cams pass each other, both the springs 6| and" 63 arepermittedto expand for an instant, i. e., until the upper cam againreaches its lowermost seat against the lower cam. Of course, the pin 62against which bothsprings push is not permitted ltoward the lowerportion 42.

bit 36 into the formation; This action causes the bit to developajshatteiing and chipping action which is most effective-in eroding hardmaterial such as rock. The bit has proven to be highly eifective whensloping strata ofv hard materials areencountered. The result ofIencounteriing such sloping strata with an ordinary lrotary to moveupwards, be'cause of the fact that it is -held at its then elevation bybeing rigidly connected to the lower en d of the drill stem; hence theonly effect of the spring 6| is to push the upper portion 43 of the bodyrapidly downward The spring 63, however, being at all times undercompression between the pin 62 and the collar 66, is given aninstantaneous opportunity to push the collar 66 upward, carrying with itthe circulation tube ,61 and the lower portion -42 of the body, to whichthe tube61 is connected. This either raises the rbit 36 slightly fromthe bottom of the hole or, if not actually so raising it, relieves thepressure with which the bit bearsv against the bottom of the holesufciently to permitan increased amount of circulation fluid to washaround the cutting edges; hence the cutting edges of the bit of thepresent invention aremore adequately I 'cooled than in the case of theconventional ilshtail bit and'the detritus which otherwise tends toaccumulate at and adjacent the cutting edges is more adequately washedaway by the relatively rapidly moving fluid. Accordingly, the bit of itobe' rotated .f

tion is less than thatwhich can be overcome by the action of the springs6| and 63, the bit 36, even if it should become firmly rlodged in theformation being drilled so as to remain stationv ary, will not cause thetwisting off of the vdrill stem. Instead, in all probability it willwork itself loose, because of the then exceedingly rapid rat at whichpercussive blows would be imparted to the bit. Moreover, vthe operator,being informed of the fact that -the bit is no longer rotating becauseAthe shock of each percussion is' y made manifest to him, -bothby soundand by feel,

bit-isto cause the bit to be deflected from vthe will permit .no furtherpay-out of drill stem yuntil the bit has chipped its'way clear again.

`Although as statedjthe shock of each percussion is transmitted tcracertain degree through til Cil

the operator informed `of the character of the formation being drilled,this shock is not so great as to endanger the crystalline structure ofthe material of which the drill pipe and rotary are constructed. Suchshock is transmitted from the body of the drill to the drill stem,through the springs 6l and |53, which therefore act in the capacity ofshock absorbers, diminishing this reactive force to a very great degree.

The respective strengths of the two springs 6l and 63 are such that thedrill is self regulating, at least to a certain measure. Regardless ofthe man ner inwhich the drilling operator controls the rate at which thedrill stem is lowered, the drill will compensate for variation in thecharacter of the formation being drilled. As stated, when drillingthrough soft material, the bit will freely rotate, and when hardermaterial is encountered, the bit will itself, and without any effortonthe part of the operator, develop the percussive chipping action of thebit s'o't'hat the drilling in that type of material progresses withthetype of motion'of the bit which is most advantageous in eroding thatparticular type.

I claim:

1. In a drilling tool, a body, coupling means for attaching one end ofsaid body to a drill stem, a bit carried at the other end of said body,said body comprising a driving portion connected to said coupling meansto be rotated thereby as said drill stem rotates and a driven portionconnected to said driving portion but revoluble with respect thereto,inter-engaging upper and lower cams interposed between said two portionswhereby said driven portion is rotated with saiddriving portion so longas 'longitudinal movement of either portion with respect to the other isprevented, yielding means pressing said upper cam downwards against saidlower cam, and yielding means pressing said lower cam and bit upwardstoward said upper cam and tending to lift said bit just after thepassage of the crests of the cams pastI each other.

2. In a drilling tool, a body comprising a lower, driven portion, meansfor securing a bit to the i lower end thereof, andrcam-means on theupper end of saidlower body portion, and an upper, driving portion,cam-means on the lower end thereof interengaged with saidfirst-mentioned cam-means whereby said driven portion is rotated v bysaid driving portion so long as they are not permitted to separate, atube rigid with said upper body portion, another tube telescopicallyengaged therewith, spline means interconnecting said tubes for rotationtogether and longitudinal movement with respect to each other, means forconnecting said second mentioned tube to a drill stem, and resilientmeans under compression between said second mentioned tube and saidupper body portion.

3. In a drilling tool, a body comprising a lower, driven portion, meansfor securing a bit to the lower end thereof, and cam-means on the upperend of said lower body portion, and an upper, driving portion, cam-meanson the lower end thereof` interengaged with said first-mentionedcam-means whereby said driven portion is rotatedv by said drivingportionso long as they are not permitted to separate, a tube rigid with saidAupper body portion, another tube telescopically engaged therewith,spline means interconnecting said tubes for rotation together andlongitudinal movement with respect to each other, means for connectingsaid second mentionedtube to a drill stem, means providing anabutmentrigid with the lower end of said second 'mentioned tube, and a springVunder compression between said upper body portion and said abutment.

4. In a drilling tool, a. body comprising a lower, driven portion, meansfor securing a bit to the lower end thereof, and cam-means on the upperend of said lower body portion, and an upper driving portion, cam-meanson the lower end thereof interengaged with said first-mentionedcam-means whereby said driven portion is rotated by said driving portionso long as they are not permitted to separate, a tube rigid with saidupper body portion, another tube telescopically engaged therewith,spline means interconnecting vsaid tubes for rotation together andlongitudinal movement with respect to each other, means for connectingsaid second mentioned tube to a drill stem, means providing an abutmentrigid with the lower end of said second mentioned tube, a spring undercompression between said upper body portion and said abutment, a tensiontube secured at its lower end to said lower body portion, and extendingupwards through said upper body portion and through said abutment, meansproviding an abutment rigid with said tension tube, and a spring undercompression between said two abutments.

5. In a drilling apparatus, a drill column adapted to be extended into awell and rotated therein, a bit carried thereby, resilient meansinterposed between said column and said bit and transmitting weight ofsaid column to said bit, means actuated by said column in rotating forimparting percussion to said bit, tension means connected to said bitand extending upwards therefrom, and a spring interposed between saiddrill column and said tension means and pulling saidbit upwards towardsaid column.

6. In a drilling tool, a body portion adapted to be extended into a welland rotated therein, a bit carried by said body portion in position tobe rotated thereby against the bottom of said well, means within saidbody portion and actuated by rotation thereof for imparting percussionto said bit, and means within said body portion providing a reservoiryfor lubricating oil, said reservoir being in communication with saidpercussionimparting means whereby saidpercussion-imparting means arefloodedin a bath of oil at all times during operation of said drillingtool.

7. In a drilling tool, a. body portion adapted to be extended into awell and rotated therein, a bit carried by said body portion in positionto be rotated thereby against the bottom of said well, means within saidbody portion and actuated by rotation thereof for imparting percus-.sion to said bit, means within said body portion providing areservoir'for lubricating oil, said reservoir being in` communicationwith said percussion-imparting means whereby said percussion-impartingmeans are flooded in a bath of oil at all times during operation of saiddrilling tool, and means providing a by-pass for conducting circulationfluid past said reservoir and vpercussion-imparting means to said bitwithout contaminating said lubricating oil.

8. In a drilling apparatus, a drill column adapted to be extended into awell and rotated ment and said extending means-to said bit upwards.

bysaid drill colunm and said lower cam member being rigid with said bit,and resilient means urging said cam members yieldably against each otherwhereby the lowerI cam memberl and bit are urged to rotate by said uppercam member but said cam members are permitted'to move away from eachother and override when said upper cam memberrotates with respect to thelower, lubricantwithin said housing and floodlower cam members disposedwithin said nous-1 ing, said upper cam member being carried by saiddrill column and said lower cam member being rigid with said bit, andresilient' means urg-' ing said cam members yieldably against eachf 12.In a drilling tool, a drill column,r means 4 providing' an abutmentrigid with the lower end thereof, a coupling, means connecting said cou.

pling to said abutment to be rotated thereby but permitting relativeaxial movement therebetween, an upper cam rigid with said coupling, aylower cam cooperatively engaged therewith and revoluble with respectthereto whereby said cams are enabled to override, a bit carried by saidlower cam, a spring under compression between said other whereby thelower cam member and bit are urged to rotate by said upper cam memberbut said cam members are permitted to move away from each other andoverride when said upper cam member rotates with respect to the lower.lubricant within said housing and vflooding said cam members, .packingmeans sealing said housing against flow of liquid into or out of saidhousing, and means'providlng a by-pass for conducting circulation fluidfrom said drilling column past said cam members to said bit without conltaminating sa'id lubricant.

10'. In a drilling apparatus; a drill column 'adapted to be extendedinto a well and rotated therein,y a tubular housing. suspended onthelower end thereof, a drilling bit, means for mounting said bit upon'thelower end of said housing, said bit being movable both axially and saidabutment and extending downward there-.

abutmentand said couplingA whereby downward pressure ofsaid column isimposed upon said bit except at the instant followingv overriding of thehigh points of said cams past each other, a tube rigid with said bit andextending upwards therefrom past said .cams and abutment, said bithaving a passage therein communicating with said'tube and leadingthrough said bit to deliver uid to the working parts thereof .and the'upper end of said tube communicating with the bore of .said column toconduct uici' to saidbit therefrom, means providing .anabutment'adjacent the upper end of said tube, and a spring undercompression between saidabutments and urging said bit toward said drillcolumn.

13. In a drilling tool, a drill column, means' providing an abutmentrigid with thelower end thereof, a tube having a splined connection withpast, a couplingrigid with the lower endof said tube, an upper cam rigidwith said coupling, a

lower cam cooperatively engaged therewith and revoluble with respectthereto whereby said cams are enabled to override, abit carried by saidlower cam', a spring under compression between said abutment andsaidcoupling whereby down# ward pressure of s'aid column is imparted to said'bit except at theinstant following overriding of revolubly with respectto said. drill column, oo-

operating upper and lower cam members disposed within said housing, saidupper cam mem- 'ber being carried by said drill column and said lowercam member being rigid with said bit, and resilient means urging saidvcam members yieldably against each other whereby the lower cam -memberand bit`aie urged to rotate by said upper -cam member but s aid cammembers are pennitted to move away from each other and-override whensaid upper cam member rotates with respect to the lower, and a springinterposed between saiddrill column and said bitand urging `said bitupwards .away from the bottom of said well.

1l. In 'a drilling tool, a drill column, means providing an abutmentrigid with the lower end thereof, a coupling, means connecting saidcoupling to said abutment to be rotated thereby but vpermitting relativeaxial movement therebe- 1' said abutmentl and extending downwardtherethe high points of said cams past each other, a circulation tuberigid with said bit and extending upwards therefrom through said camsand abutment, means on said circulation tube providing an abutment abovesaid rst mentioned abutment, and a spring under compression between saidabutments.

14. In a drilling tool, a'drill column, means providing an abutmentrigid with the lower vend thereof, a tube having a splined connectionlwith past, a coupling rigid with the lower end of said tube, an uppercam rigid with said coupling, a I `lowercaln cooperatively engagedtherewith and revoluble with respect thereto whereby said cams areenabled to override, a bit carried by said lower cam, a spring undercompression between said.

abutment and said coupling whereby downward pressure lof said column isimparted to said bit except at the instant followingoverriding of thektween, lan upper cam rigid with said coupling',

tween said abutment and said coupling wherebyv downward pressure of saidcolumn is imposed upon said .bit except at the instant following highpoints of said cams past each other, a circulation'tube rigid 'with saidbit and extending upwards therefrom through said cams and abutment,means on said circulation .tube providing anabutment above said firstmentioned abutment.. a spring under compression between said .abutmentameans closing the upper'end of said 1 splined tube andenclosing saidsecond mentioned overriding 'of the high points of said cams past eachother, means rigid with said bit and extendi'g'therefromipast saidabutment, and a spring under/ compression between said abutspring, saidsplined tube and said closing means lubricant within said. reservoir.

therefor cooperating to define a reservoir, and

15. In a drilling tool, a drill column, meansi yproviding an abutmentrigid with the lower end thereof, a tube having a splined connectionwith; said abutment' and extending downward therelower cam cooperativelyengaged therewith and revoluble with respect thereto whereby said camsare enabled to override, a bit carried by said lower t cam, a springunder compression between said abutment and said coupling wherebydownward pressure of said column is imparted to' said bit except at theinstant following overriding of the -high points of said cams past eachother. a cir.- culation tube rigid with said bit and extending upwardstherefrom through said cams and abutment, means on said circulation tubeproviding an abutment above said rst mentioned abutment, a spring undercompression between said abutments, means closing the upper end of'saidsplined tube and enclosing said second mentioned spring, said splinedtube and said closingmeans therefor co-operating to define a reservoir,and lubricant Within said reservoir. said coupling having a passagetherethrough whereby said lubr-icant is conducted to said cams.

l,16. In a vdrilling tool, a drill column, vmeans providing an abutmentrigid with Vthe lower end thereof, a tube having a splined connectionwith said abutment and extending downward therepast, a coupling rigidwith the lowerend of said tube,` an upper cam rigid with said coupling,a

'lower 'cam cooperatively engaged therewith and .cover tube.

revoluble with respect thereto whereby said cams are enabled tooverride, a bit carried 'by said lower cam, a spring under compressionbetween said abutment and said coupling whereby downward pressure ofsaid column is imparted to said bit except at the instant followingoverriding ofthe high points of said cams past each other, a circulationtube rigid with saidbit and extending upwards therefrom through saidcams and abutment, means on said 'circulation tube providing an abutmentabove said rst mentioned abutment, ya. spring under compression betweensaid abutments. means closing the upper end of said splined tube andenclosing said second mentioned spring, said splined tube and said,closing means therefor cooperating to denne a reservoir. lubricantwithin said reservoir, said coupling having a passagey therethroughwhereby said lu fbricant is conducted to said cams, a cover tube rigidwith said bit and extending upwards therefrom past and ,enclosing saidcams, coupling,

splined tube and its closing means, and packing means sealing the upperend of said cover tubebut permitting relative motions between it andsaid drill column, said splined tube and its closing means havingopenings therein for the flow of lubricant to the space between them andsaid GARY E. PREBENSEN.

